By Christopher Lim
Have you ever been walking along the shoreline and seen green patches of vegetation in the water? That’s most likely eelgrass, Zostera marina, an underwater flowering plant that lives directly in the bay. Eelgrass is not simply another plant though; its effects on the San Francisco Bay are vital for a healthy ecosystem.
Eelgrass is a survivor. Even though the water of San Francisco Bay is turbid, or cloudy, eelgrass still finds a way to photosynthesize and live in the shallows of the estuary. While the historical distribution of eelgrass in the Bay is unknown, there is currently a movement to restore eelgrass beds to our waters because of their various environmental benefits.
Eelgrass beds provide shelter and food for many forms of life. Some fish use the eelgrass for protection from predators while others use it as a permanent shelter to spend their entire lives. Some fish, like herring, use eelgrass as a nursery to lay their sticky eggs. Small invertebrates such as crabs, sea snails, amphipods and crustaceans can also make their home in eelgrass. You can see the food web in action among the eelgrass beds: larger animals often come by to feed on the smaller animals grazing in the eelgrass.
The Richmond Shoreline is a special place for eelgrass. There, the largest remaining patches of eelgrass in the San Francisco Bay grow relatively undisturbed and unnoticed. This hidden treasure highlights the diversity and importance of the Richmond Shoreline in the larger scheme of San Francisco Bay subtidal habitat restoration.
The Watershed Project is currently developing the groundwork to initiate the construction of a “living shoreline.” This program approaches the shoreline from a holistic viewpoint, incorporating inland areas all the way to the subtidal waters below the shoreline. According to the San Francisco Bay Subtidal Habitat Goals Project, “These techniques reinforce the shoreline, minimize coastal erosion, and maintain coastal processes while protecting, restoring, enhancing, and creating natural habitat for fish and aquatic plants and wildlife.” This living shoreline approach creates the interconnections found in any healthy ecosystem.
Two of the main players in the Living Shoreline concept are eelgrass and oysters. When grown near each other, these two work together as a team. Oysters are filter feeders. Over the course of a day, a single oyster can take in 50 gallons of seawater and filter out microscopic bits of food, which in turn helps to clarify the water. Remember, eelgrass is a plant, so clearer water means more sunlight can penetrate deeper, which means healthier habitat for eelgrass. Combine these biological processes with the physical structures of a Living Shoreline (such as oyster reef balls) and you’ve got the makings of a restored habitat capable of supporting a robust community of subtidal life.
Photo credits (from top): Chris Lim, NOAA, Washington State University.